Treatment of copper minerals



Patented May 15, 1928.

UNITED STATES PATENT OFFICE- IIOUIS F. CLARK, OF GRAND RAPIDS, MICHIGAN, ASSIGNOR TO UNION CARBIDE SALES COMPANY, OF NEW YORK, N. Y., A CORPORATION OF WEST VIRGINIA.

TREATMENT OF COPPER MINERALS.

No Drawing.

The invention is a process for recovering with sulphur sometimes give poor recoveries when flotation is applied to them. This may be due to superficial oxidation, or to less understood causes connected with the nature of the minerals with which the sulphite is associated in the ore. The process to be described gives increased amenability to fiotation when applied to many copper minerals and particularly to those which are not adapted for flotation concentration by standard methods.

Copper minerals in an ore may be so closely associated, either by chemical combination or physical proximity, with the minerals of other metals, that a process intended to make a copper mineral floatable may also aid in the flotation of the other,

minerals. But if such close association does not exist it is possible by a proper use of my' invention to select only the copper minerals in the ore and to separate them from the other minerals.

Copper minerals may be classified as cupric and cuprous depending on the state of oxidation of the element. Both these classes are amenable to the treatment herein described.

I have found that cupric copper inalkaline, neutral or slightly acid solution, in the presence of acet lene, becomes an oxidizing agent because 0 its tendency to precipitate as' a cuprous compound, cuprous acetylide. In order to produce this effect an oxidizable compound must also be present. This oxi dizable compound may be acetylene itself,

or some other oxidizable substance either organic or inorganic, for'example carbon monoxide or glucose. In some cases it is advantageous to use an oxidizable substance which can be converted into an insoluble Application filed October 29, 1923. Serial No. 671,892.

compound, such as a resin, by oxidation. Examples of this class of compounds are aniline, linseedoil, turpentine, and pine oil. Under suitable conditions the insoluble organic oxidation product is precipitated with the cuprous acetylide.

I have applied the above principle to the treatment of copper minerals, es ecially the oxide minerals, in an ore pulp. guch copper minerals, in a water pulp in' the presence of dissolved acetylene, are able to oxidize at.

their surface any oxidizable compound simultaneously dissolved. Thus a coating takes place on the surface of the copper mineral. primarily of the compound cuprous acetylide. If for example aniline, or turpentine, are also present dissolved in the water, then a composite coating is produced (a). The hydrogen ion concentration of the water used to make up the pulp, together with the influence of dissolved salts. This determines the extent to which the copper minerals may be superficially attacked so as to render them more amenable to the coating reaction and it also influences the ra idity of the coating reaction itself. T us,

slightly acid pulps may be desirable with some ores. Slig tly acid is here intended generally to express an acidity caused by the hydrolysis of a weak-base salt, e. g. ferrous sulphate. Free sulphuric acid might also be present in traces, but although it might help to attack the minerals, it might delay the required coating action andeventually might prevent it entirely. This is because the coating reaction itself makes acid by hydration and oxidation of the acetylene to acetic acid. On the 0 'her hand alkaline pulps may be desirable. The alkalinity may be brought about by addition of lime or soda ash or caustic soda. gaiimtly also addition of ammonia is help- These reagents tend to film the copper Fresilicates and other compounds with co per hydroxide which is itself especially a aptable to the coating reaction. Again, a combination of these conditions may be useful, as, for example, a treatment first with a weak solution of ferrous sulphate or sulphuric acid, followed by addition of alkali and the coating reagents. Also, the addition of other reagents may be useful for both purposes, e. g. sodium silicate, phosphate, chloride and so forth.

(b). The temperature of the solutions together with the concentration of the various substances dissolved 'are important. In general, especially if an alkaline pulp is used, a warm solution'is better than a cold one. Particularly it might be advantageous to heat an alkaline pulp during the operation of grinding so as to, increase the formation of hydroxide on the surfaces of the mineral particles. On the other hand, warming the ulp decreases the solubility of the most important element of the coating reagents, viz, the acetylene. Thus if a warmpulp is used it may be necessary to enclose it and inject acetylene gas under pressure.

' The time during which the reagents are allowed to act upon the mineral particles is also important. Both'the action of the surface attack on the mineral particles and the coating effect itself, are rather slow in operation. Warming the pulp seems to reduce'the time required.

. The preceding paragraphs have spoken perhaps too definitely of two phases of the procedure; first the attack on the surfaces of the mineral particles, and then the coating effect. In reality in operation it would be diflicult to say when one of these took place andthe other began or to tell their comparative extent. Similarly the whole coating result on one mineral might be quite different from that on another, and yet both give good flotation. In one case a coating very heavy and black might be required and in other an efiect not visible to the naked eye would be suflicient for satisfactory flotation. a

It should also be noted that this coating y the action of acetylene implies the injection and dissolution of the as in the liquid of the pul After suflic ent action has taken place t e excess gas may be removed from solution by heating the pulp or applying a vacuum.

' is process of coatin the copper mine erals in an ore pulp for iIotation concentration may in general. be applied with the regular machinery now in use for such ore dressing.

An ore may be ground with a. cold solution of lime, ammonia, pine oil, a flotation oiling oil and acetylene as. After grinding such a pulp mi t well be partially dehydrated or thickened to reso increase considerably the time available for the coating operation to reach a satisfactory condition. Such a thickened pulp would then be diluted with other water for the flotation operation.

An ore may be ground with a warm solution of caustic soda, ammonia, glucose and a flotation oiling oil. The warm 1 to 1 pulp may be collected in a container and then acetylene gas injected so that the. whole is under pressure. The pulp should then be diluted with cold water and classified. Particles which had not been finely ground in the first instance would then come through again for further coating.

An ore may be ground with a cold solution of ferrous sulphate, aniline, acetylene and a flotation oiling oil. Later in its progress such a pulp may, or not, be made alkaline, say with lime and the flotation operation carried out. The tail pulp from such an o erat-ion should be settled to recover valua le solution for reuse on fresh charges of ore.

' In any or all of these cases the flotation oils may be omitted or applied at other points in the scheme of operation. Likewise the injection of the acetylene to form a solution of the gas in the pulp may be effected at any convenient point and by suitable means, as for example blowing the gas also carried N aOH, 1 pound per ton of ore,-

and NH 0.80 pounds per ton. Temperature of pulp during grinding was 50 C. After grinding, the mixture was transferred to an autoclave using 1200 grams more of water as a wash, thus giving a 2 to 1 pulp. Now 1 pound more of N aOH per ton of ore and 0.80 pounds more of NH were added, together, with two pounds per ton of ore of aniline oil. Acetylene gas was now injected while the pulp was agitated and held at about 50 C. A pressure of about 25 pounds per square inch was maintained. At the end of about 15 minutes 'the coating eration was completed and the excess gas b own ofl. The pulp was now diluted with cold water to a 5 to 1 ratio and flotation conducted in a mechanically agitated machlne using coal tar, creosote and pine oil.

The following results were obtained;

Feed-2.10% total copper. Feed2.00% oxide copper. Qoncentrate14.50% total copper. Concentrate-11.30% oxide copper. Tails0.7-7% total copper. Tails0.7 3% oxide copper.

Recovery on total copper, 65.40 per cent. This example indicates what might be expected when comparatively large amounts of the reagents are applied in warm solution for a short time. 011 large scale work and where operation might be made continuous in such an apparatus as has been mentioned wherein the gas may be injected and recovered from the pulp as it passes through a pressure'container, more thorough coating may be expected and accordingly better flotation results.

In another example 1200 grams of 20- mesh ore were ground 30 minutes with 1200 ams of water which contained 0.80 pounds of NH and 1 pound of NaOH per ton of ore. A temperature of 50 C. was maintained during grinding. After grinding, the pulp was cooled to about 15 (J. and 1200 grams of cold water added. This last water carried aniline oil and acetylene dissolved amounting to 1 pound of each per ton of ore. The pulp was agitated and then allowed to stand in the liquid for 24 hours. It was then diluted and flotation carried out as before noted.' The following results were obtained.

Feed2.09% total copper.

2.00% oxide copper. Concentrate20.90% total copper. 18.70% oxide copper. -Tails0.79% total copper.

0.73% oxide copper.

Recovering on total copper, 62.00 per cent. This exam 1e illustrates the use of lesser amounts 0 reagentsin cold solution where the coating action was allowed to, proceed through considerable time. This indicates also the application before mentioned of a thickening device which would at once recover excess solution from the pulp and delay the advance of the solids until sufficient coating action had taken place.

This principle may be extended to a system of tank storage of thickened pulp containing smallamounts of the required reagents dissolved. Coating act1on may be thus carried out over periods of days without reducing the tonnage capacity of the.

milling plant. In such a case, however, and especially where an alkaline solution is used. the pulp' had best be protected as much as possible from sun light and air which would tend to cause consumption of acetylene by diiferencebetweenthe coating action of acetylene and of hydrogen sulphide. The latter coats indiscriminately iron, lead, copper and so forth and is thus largely consumed by Worthless minerals. I

\Vhere the orcs contain minerals of other metals than copper, most commonly iron, lead and zinc, the treatment described has a selective action. It acts only on the particles of the copper minerals 'prcsent sothat in the subsequent flotation it is only, or mainlythe copper minerals which will be floated; so that the latter only will be selected and separated from other metals.

For the flotation operation to which the treated ore is subsequently subjected, any usual or suitable flotation oils and methods may be applied. I The treatment may be used also to recover by flotation other elements which .may be closely associated with the copper minerals where the floatability of the particles is sufliciently great to'carry the percentage of the'other elements present in the particles.

WVhe-re the ore contains mixed oxides and sulphides of coppe'r it may be subjected first to a flotation operation on the pulp to remove the sulphides of copper (or in fact any other minerals which are naturally floatable) after which the present process may be applied to the residue carrying oxides of copper or other diflicultly floatable copperto the particular embodiments described. Various modifications in the steps of the process and in their'order and in the proportions ofthe ingredients stated may be made by those skilled in the artwithout de-. I parting'from the invention as defined in the followm claims.

What claim is a 1. The method of treating ores containing copper minerals to increase their susceptibility to flotation concentration by processes dependent upon afiinity between minerals and a gaseous agent which consists in applying to 'apulpof the ores. acetylene and other oxidizable substances, the oxidation of which results in insoluble substances thus producing on the particles of the said minores containing copper minerals to increase their susceptibility to subsequent flotation concentration by processes dependent upon afiinity between minerals and a gaseous agent.which consists in applying to a pulp of the ores acetylene gas under pressure,

the temperature of the pulp being too high to retain a substantial quantity of gas at atmospheric pressure.

4. The process which comprises treating a copper ore with acetylene until the floatability of the copper mineral is materially increased, and then floating the mineral, by froth flotation.

5. The process which comprises treating a pulp of copper ore with acetylene until the floatability of the copper mineral is materially increased, and then floating the mineral, by froth flotation. I

6. In a process of concentratin copper ores, the ste of treating a pulp the ore with acetylene until the floatability of the copper mineral by processes dependent upon affinity between minerals and a gaseous agent is materially in'creased..

7. The process which comprises rendering a pulp of copper ore alkaline; adding a nongaseous reducing agent; treating the pulp with acetylene until the fioatability of the copper mineral is materially increas'ed. and

then floating the mineral, by froth ,flotation.

8. The process which comprises rendering a pulp of copper ore alkaline; adding an organic reducing agent adapted to form a water-insoluble oxidation product; and treating the pulp with acetylene until the floatability of the copper mineral by processes dependent upon aflinity between minerals and a gaseous agent is materially increased. I

, 9. The process which comprises rendering a pulp of copper ore alkaline; adding aniline; treating the pulp with acetylene until the floatability of the copper mineral is materially increased, and then floating the mineral, by froth flotation.

In witness whereof, I have hereunto signed my name.

LOUIS F. CLARK. 

